The population of the system is a factor for it as well, but the way its implemented it is quite useless.
In general the BGS is transaction based, with a modifier for the value based on the system's population size.
This is what helps determine two things; how much influence gains in a given system per transaction, and how much extra work is boosted - case in point Bonds and Bounties as well as Trade.
The downside is an apparent cap of how much you can boost the transaction - so in the end three 100k bonds end up counting more than one million bond.
It has a current flaw with how Superpower Bounties are split now, as the split difference is so insignificant compared to the fact that several factions get boosted - to which having 3 or more similar supwerpower-aligned factions in a system is a net negative for the controlling faction.
A similar effect has occurred which is why in the past single-item transactions could boost influence through trade by selling 700x 1 ton items.
It has been patched so a stack of items is counted as a whole if they are all picked up from the same location.
There remains that modifier based off profit, but its back to it making the value moot - as selling three different items counts more than selling a whole cargo load of something very profitable.
Bottom line; it ends up not being how much you do at once, but how many you end up handing in over time.
If FDev were to ever patch it to have the value modifier work again it may be nice, but I don't see that happening as it would leave it incredibly easy for controlling factions in Haz Rez sites or good Trade routes to expand endlessly.
